The long range objective of this project is to elucidate the mechanisms by which the physiological action of opioid peptides is terminated. The research will focus on the role of two peptidases, a neutral endopeptidase and an enkephalin degrading aminopeptidase, as "enkephalinases". The neutral endopeptidase has been shown to exist in multiple forms in kidney and brain. A cDNA clone to the neutral endopeptidase will be isolated. The cDNA will be used to probe brain mRNA for the existence of multiple messages for the enzyme. In addition, the cDNA will be used to determine the amino acid sequence of the enzyme. In conjunction with these studies, the nature of the multiple forms of the enzyme will be investigated by biochemical techniques with particular emphasis on the carbohydrate structure of the enzyme. Studies will also be conducted of the effects of non-opioid peptides on the degradation of opioid peptides. These studies will focus on the ability of non-opioid peptides to inhibit the neutral endopeptidase and the enkephalin degrading aminopeptidase. The latter enzyme will be characterized in terms of its localization in brain and its relationship to other aminopeptidases. Lastly, the pathways for degradation of the dynorphins will be studied in crude brain membrane fractions. The degradative pathways will be established, and the peptidases involved will be partially purified and characterized.